Six areas of theoretical population genetic research are to be developed. Studies of linkage and fertility selection, including the properties of genetic modifiers of recombination will be continued. Models of mixed inbreeding and outcrossing, appropriate to plant population genetics, will be constructed. The interaction of the mating system with epistatic selection and population subdivision will be elucidated for one and two gene systems. Exact analysis of the question of optimal mutation rates is our third area of research. The fourth concerns whether the even sex ratio, previously shown to be genetically optimal when sex is controlled by a single gene, is optimal with more complex sex determination. Our studies of cultural transmission and evolution will include both evolutionary modelling and data analysis of traits of mixed genetic and cultural etiology. Finally we continue our exact genetic modelling of kin selection with two linked loci and in subdivided populations.